1. Field of the Invention
The invention relates generally to a flexible platform that generates aerosols and vapors through the volatilization of a liquid for laboratory testing and development of applications for volatilized liquids.
2. Description of Related Art
U.S. Pat. No. 5,743,251, which is incorporated herein by reference, discloses an aerosol generator that includes a tube having a first open end. The aerosol generator further includes a heater for heating the tube to a temperature sufficient to volatilize material in a liquid form in the tube such that the volatilized material expands out of the open end of the tube and mixes with ambient air to form an aerosol.
An aerosol generator 21 according to U.S. Pat. No. 5,743,251 is schematically shown with reference to FIG. 1. The aerosol generator 21 includes a tube 23 having an open end 25. A heater 27 is positioned adjacent to at least a portion of the tube 23, but preferably in a way that provides a heated zone around the tube that maximizes heat transfer evenly throughout the heated zone. The heater 27 is connected to a power supply 29, preferably a DC power supply, such as a battery.
In operation, a material (not shown) in liquid form is introduced to the tube 23. The heater 27 heats the portion of the tube 23 to a sufficient temperature to volatilize the liquid material. In the case of an organic liquid material, the heater preferably heats the liquid material just to the boiling point of the liquid material, and preferably maintains the surface temperature of the tube 23 below 400 xc2x0 C., as most organic materials are not stable when they are exposed to temperatures above that temperature for periods of time. The volatilized material expands out of the open end 25 of the tube 23. The volatilized material mixes with ambient air outside of the tube and condenses to form particles, thereby forming an aerosol.
The tube 23 is a capillary tube or a portion thereof having an inside diameter of between 0.05 and 0.53 millimeter and the inside diameter of the tube can be approximately 0.1 millimeter. The tube 23 can be a portion of a fused silica capillary column, an aluminum silicate ceramic tube, or other substantially non-reactive materials capable of withstanding repeated heating cycles and generated pressures and having suitable heat conduction properties. If desired or necessary, an inside wall of the tube 23 may be provided with a coating for reducing the tendency of material to stick to the wall of the tube, which may result in clogging.
The tube 23 may be closed at a second end 31 and material in liquid form may be introduced into the tube 23 through the open end 25 when it is desired to form an aerosol. Thus, when the liquid material is heated by the heater 27, the volatilized material is only able to expand by exiting the tube 23 through the open end 25. However, the second end 31 of the tube is connected to a source 33 (shown by dotted lines in FIG. 1) of liquid material. The liquid material in the portion of the tube 23 volatilized by the heater 27 is prevented from expanding in the direction of the second end 31 of the tube, and is forced out of the open end 25 of the tube, as a result of back pressure of liquid from the source 33 of liquid material. The back pressure of the liquid is between about 20 to 30 psi.
It is contemplated that a variety of uses can be developed for the aerosol generator described above. In order to investigate such uses, it would be desirable to have an instrument capable of generating vapors and aerosols to be evaluated.
The invention provides a programmable instrument for volatilizing liquid material, thus facilitating investigational use of the vaporized liquid for various applications.
A material in liquid form is supplied to a flow passage and the liquid material is heated to a temperature sufficient to volatilize the material such that the material expands out of the flow passage, which results in a vapor of the volatilized material, the volatilized material, then if desired, condensing upon mixing with air to form an aerosol. A programmable controller is used to control delivery of liquid material to the flow passage and/or control heating of a heater arrangement for volatilizing the liquid.
An embodiment is directed towards an instrument and method for generating an aerosol with a flow passage defined by a metal tube capable of conducting electricity. The tube has a first open end and a power supply for supplying power to a heater comprises a section of the metal tube such that the tube heats to a temperature sufficient to volatilize the liquid material in the flow passage. The volatilized material expands out of the open end of the flow passage and then may mix with ambient air to form an aerosol.
Another embodiment is directed towards an instrument and method for generating a volatilized liquid comprising a flow passage having a first open end and a heater which heats the flow passage to a temperature sufficient to volatilize material in liquid form such that the volatilized material expands out of the open end of the flow passage. The volatilized material may then mix with ambient air to form an aerosol. A controller is operable to maintain the temperature of the flow passage and regulate the flow of material. The controller is preferably capable of accepting manually entered commands or programs associated with operating parameters of the instrument. In addition, the controller is configured to be programmed for different parameters associated with the generation of the aerosol and/or precursor vapor, such that the controller can be used for developmental testing.
A further embodiment is directed to an instrument and method for generating a volatilized liquid including a flow passage with a first open end and a plurality of heaters for heating the flow passage to a temperature sufficient to volatilize material in liquid form in the flow passage such that the volatilized material expands out of the open end and may mix with ambient air to form an aerosol.
A method for generating an aerosol or vapor comprises steps of setting a target parameter, such as resistance of a heater arrangement, such as a resistance heater, corresponding to a temperature sufficient to volatilize a liquid material within a flow passage heated by the heater; supplying a liquid material to the flow passage; periodically determining the parameter of the heater; comparing the parameter to the target parameter; and energizing the heater when the parameter is less than the target parameter. In other embodiments, the method comprises setting a series or range of target parameters (i.e., multiple or variable target parameters), such as a series or range of resistance values of a heater.
Another embodiment is directed to an instrument for generation of volatilized material, which comprises at least one flow passage having an open end; a liquid supply operable to supply liquid material to the flow passage; at least one heater adapted to heat the flow passage to a temperature sufficient to volatilize material in liquid form in the flow passage such that the volatilized material expands out of the open end of the flow passage, the volatilized material optionally being admixed with air to form an aerosol; a first flow path in fluid communication with the open end of the flow passage; a second flow path in fluid communication with the open end of the flow passage, the second flow path being different from the first flow path; a first valve in fluid communication with the open end of the flow passage; and a controller operable to monitor a condition of the heater and to control operation of the first valve such that the volatilized material or aerosol (i) flows through the first flow path when the heater is in a non-conforming condition and (ii) flows through the second flow path when the heater is in a confirming condition.